1. Field of the Invention
This invention relates generally to the formation of a single crystal ribbon and more particularly is directed towards a novel method and associated apparatus for the continuous formation of silicon crystal ribbons.
2. Description of the Prior Art
Single crystal semiconductive wafers for various electronic applications typically have been grown in the form of rods by pulling a seed crystal slowly upwards from a pool of molten silicon. The rod, once formed, is then sliced into thin wafers which again may be cut into smaller semiconductive components. This procedure is quite slow and expensive in view of the fact that much of the material is wasted in the cutting operation. In order to eliminate some of the problems inherent in the vertical pulling techniques, considerable effort has been directed towards forming the semiconductive material directly into a ribbon, thereby eliminating the waste and time involved in cutting rods into wafers. A thin, monocrystalline ribbon, once formed, may then by suitably scored in the desired pattern and the several elements broken away from the ribbon for component use.
While the thin ribbon could be drawn directly through a slot in a die in a vertical direction above a pool of molten material, the procedure is extremely slow. More recent efforts have been directed towards the pulling of a ribbon horizontally from the surface of a pool of molten semiconductive material which technique provides a greater solid/liquid interface area of crystal formation and, hence, is more productive than vertical crystal growing procedures. However, the techniques and the apparatus utilized heretofore in the growing of monocrystalline semiconductive ribbons using the horizontal pulling procedures have not been satisfactory from the standpoint of quality, uniform thickness and width and operating stability.
Accordingly, it is an object of the present invention to provide improvements in the method and associated apparatus for forming crystalline, semiconductive ribbons on a continuous basis.
Another object of this invention is to provide a novel method and associated apparatus for producing high quality semiconductive ribbons at a high rate of production and of uniform dimensions.